ensure lnurls are actually lnurls

Changelog-Fixed: Check for broken lnurls

damus/Nostr/Nostr.swift

@@ -110,6 +110,10 @@ struct Profile: Codable {
             return lnaddress_to_lnurl(addr);
         }
         
+        if !addr.hasPrefix("lnurl") {
+            return nil
+        }
+        
         return addr;
     }